Induction-type alternating-current relays



.lune 26, 1956 w. K. soNNEMANN 2,752,539 K INDUCTION-TYPE ALTERNATING-CURRENT RELAYS Filed March 5, 1952 2 Sheets-Sheet l wlTNl-:ssi-:s: ./W/ William K.Sonnemonn.

ATTORNEY INVENTOR June 26, 1956 w. K. SONNEMANN 2,752,539

INDUCTION-TYPE ALTERNATING-CURRENT RELAYS Filed March 5, 1952 2 Sheets-Sheet 2 (0 D 3 U 0 en C l t l l I l l l 3 5 6 7 8 9 IO 2O tiples of Minimum Closing Current WITNESSES: f INVENTOR William K.Sonnemonn. BY@ Mm ATTOR N EY nited States Patent' lNDUCTIN-TYPE ALTERNATING-CURRENT RELAYS William K. Sonnemann, Roselle Park, N. J., assigner to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 5, 1952, Serial No. 274,845 Claims. (Cl. 317-167) This invention relates to devices responsive to an alternating quantity and it has particular relation to inductiontype alternating-current relays which operate with substantial time delay.

In order to facilitate the application of time-delay relays to electrical system-s for protective purposes, it has been the practice to provide relays having diiferent time-curve shapes. Examples of time curves will be found on page 117 of a book entitled Silent Sentinels, published by the Westinghouse Electric Corporation, Newark, New Jersey, in 1949.

In addition, time-delay relays are provided which are responsive to different values of minimum operating quantities such as current or voltage. The response of these relays may be controlled to some extent by the adjustment of the initial bias to which the relays are subjected. Such bias conventionally is provided by means of a spiral control spring. However, such adjustments render difficult the procurement of uniform tripping for all settings of the time levers with which such relays commonly are provided.

In accordance with the invention, a time-delay device such as a relay is provided with an adjustment through which uniform tripping current is obtained for all time lever settings. Such an adjustment may take the form of an adjustable source of bias. In addition, an adjustment is provided to permit adjustment of the relay to a minimum operating value of a quantity such as current or voltage. The adjustment preferably may take the form of a closed adjustable winding which surrounds magnetic flux produced in the relay. If the relay has an energizing winding, the adjustable closed winding may surround substantially the same magnetic flux produced by the energizing winding. Alternatively, the adjustable closed winding may surround a component of the magnetic iiux produced by the energizing winding.

ln a preferred embodiment of the relay, an E-shaped electromagnet is provided which has three pole pieces located in a common plane. An energizing winding surrounds the center pole piece Whereas a lagging winding surrounds one of the outer pole pieces. An electromagnetic armature is located adjacent the pole faces of the three pole pieces. These pole faces provide three time displaced magnetic flux components to establish a shifting magnetic field for the electroconductive armature. Independent adjustments are provided for the magnetic paths followed by two of the magnetic ux components. By manipulation of these adjustments, the shape of the time curve of the relay may be varied. Preferably, adjustable damping is providing for the electroconductive armature of the relay.

The armature of the relay is biased in a predetermined direction in a suitable manner such as by a conventional spiral control spring. Desirably, the spring is adjustable for the purpose of adjusting the bias applied to the armature.

The energizing winding may be provided with taps for thepurpose of permitting adjustment of the minimum current required for tripping. A further adjustment is provided in the form of an adjustable closed winding which surrounds magnetic flux produced by the energizing winding. This closed winding may surround one of the previously mentioned pole pieces.

It is, therefore, an object of the invention to provide an improved electroresponsive time-delay device having an adjustable minimum operating energization.

lt is a further object of the invention to provide an electroresponsive time-delay device having adjustable time delay and having a uniform minimium tripping energization for all time-delay adjustments thereof.

It is a still further object of the invention to provide a time-delay device as defined in either of the preceding two paragraphs, wherein the shape of the time curve of the device may be adjusted.

It is also an object of the invention to provide an improved method for adjusting relays.

Other objects of the invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

Figure 1 is a View in side elevation, with parts broken away and parts schematically shown, of an electrical relay embodying the invention;

Fig. 2 is a view in rear elevation, with parts schematically shown, of an electromagnet suitable for the relay of Fig. 1;

Fig. 3 is a view in rear elevation with parts schematically shown of a modied electromagnet suitable for the relay of Fig. 1;

Fig. 4 is a detailed partial view in rear elevation of an electromagnet showing an adjustable winding suitable for the electromagnet of Fig. 3;

Fig. 5 is a View in end elevation of the electromagnet shown in Fig. 4;

Fig. 6 is a view in top plan of the relay illustrated in Fig. 1;

Fig. 7 is a view taken along the line Vll-Vll of Fig. l;

Fig. 8 is a graphical representation showing certain relationships between relay torque and relay contact travel;

Fig. 9 is a graphical representation of various time curves which may he obtained by a relay embodying the invention; and

Fig. l0 is a View in perspective with parts broken away, showing a modied adjustable winding suitable for the relay of Fig. l.

Referring to the drawing, Fig. 1 shows a relay R of the type set forth in my patent application Serial No. 251,234, led October 13, 1951, now Patent No. 2,697,187, which is designed for energization in accordance with a variable alternating quantity. This relay includes a stator 1 in which a shaft 3 carrying an electroconductive armature 5 is mounted for rotation. Conveniently, the electroconductive armature 5 may be in the form of a disc constructed of aluminum or copper. An electromagnet 7 is provided for the purpose of establishing a shifting magnetic field within which a portion of the electroconductive armature 5 is located. As well understood in the art, a shifting magnetic field operates on the electroconductive armature to produce a torque urging the disc in a predetermined direction about its axis.

Preferably, adjustable damping is provided for the electroconductive armature 5. Conveniently, such damping may be provided by a horseshoe-shaped permanent magnet 9 (see Fig. 7) constructed of a high-coercive permanentmagnet material. The permanent magnet 9 has its two pole faces (identified by the reference characters N for north pole and S for south pole) positioned adjacent one face of the armature 5. A plug 13 of soft magnetic material is positioned on the opposite side of the armature to define with the pole faces two gaps within which the armature S rotates. rEhe magnet and the plug i3 may be secured to a suitable holder il of non-magnetic material such as die-cast aluminum alloy. Preferably, the plug is adjustable relative to the magnet to change the lengths of the air gaps and the strengths of the magnetic field therein. Conveniently, the plug may have screw threads in threaded engagement with threads provided in the holder il. By rotation of the plug i3, the plug may be moved towards or away from the associated permanent magnet 9 to modify the strength of the magnetic field within which the electroeonductive armature 5 rotates. As well understood in the art, such rota n of the electroeonductive ar mature provides a damping force acting between the stator to which the body or holder ii is secured and the electroconductive armature.

A spiral control spring l5 has its inner end secured to the shaft 3 and its outer end secured to a portion ot' the stator l. This spring normally is in a plane substantially transverse to the shaft 3, but is shown rotated from its normal position in Fig. l to illustrate the convoi-ations thereof. The spring occupies its normal position in Fig. 6.

A movable contact i7 is secured to the shaft 3 for movement towards and from a fixed Contact i3 which may be secured to the stator. When the relay is deenergized, the spring biases the movable contact i7 away from the fixed Contact 19. When the electromagnet 7 is sutciently energized, the movable Contact i7 is moved against the bias of the spring l5 into engagement with the fixed contact 19 to complete an electrical circuit. Such circuit completion may be employed for any desired purpose.

The time required for movement of the movable contact 17 into engagement with the fixed contact i? depends on the torque developed by the electromagnet 7 acting on the electroconductive armature 5, and on the magnitude of therdamping applied to the electroconductive armature 5 by the damping magnet assembly. The time also may be varied by adjusting the position of the movable contact 17 about the shaft 3. lf desired, the movable contact, the shaft and the disc may be adjustable as a unit by movement of a stop about the axis of the shaft to place the movable contact in any desired starting position. Such a stop E17/'B is illustrated in Fig. 6 and is well known in the art. Operation of theV stop changes the tension in. the spring i5 when the parts are in their deenergized positions.

As the movable contact i7 moves towards the fixed contact 19, the biasing torque exerted on the shaft 3 by the spring l5 increases. To compensate for such increase, the disc may have a spiral periphery which is shown in Fig. 6. it will be noted that as the movable contact 17 rotates towards the fixed contact i9, the radius of the disc 5 at the electromagnet 7 increases. Such increase in radius increases the, torque exerted on the shaft 3 by the electromagnet 7 and may be proportional to compensate for the increase in bias exerted by the spring i5. This means that if the electromagnet 7 is energized by the minimum energization required to initiate movement of the ssociated electroconductive armature in the direction of the arrow 5A, the armature will continue in substantially uniform motion as long as the energizatiou of the electromagnet 7 remains constant until the contact i7 engages the lixed contact 19.

Referring to Fig. 2, it will be noted that the electromagnet 7 includes an E-sliaped magnetic structure 2i having three pole pieces 21A, ZlB and 21C disposed substantially in a common plane. The magnetic structure 2l may be constructed of a plurality of laminations of soft magnetic material, such as soft iron, each having a shape illustrated in Fig. 2. Alternatively, each of the laminations may be constructed of two or more parts, and the parts may be associated by means of butt or inter leaved joints which are well known'in the art.

The pole pieces 21A, 21B and 21C have pole faces Zia, 2lb and 21C which are disposed in a common plane, and

Y this plane is transverse to the plane of the pole pieces 21A,

21B and 21C.

Energization of the electromagnct 7 is provided by means of a winding 23 which surrounds the intermediate pole piece 21B. Conveniently, this winding may have an adjustable number of turns as represented by taps 23A, 23B.

The winding 23 may be connected for energization in accordance with any desired alternating quantity. For example, the winding 23 may be energized in accordance with alternating voltage. However, it will be assumed that the winding 23 is energized through a current transformer 25 in accordance with alternating current flowing in a circuit represented by the conductors L1 and L2. Although the circuit may be a polyphase circuit, it will be assumed that the conductors L1 and L2 represent a singlephase alternating-current circuit operating at a power frcquency, such as 6() cycles per second.

When the winding 23 is energized, magnetomotive forces are established between the pole faces to produce a magnetic eld in the area occupied by a portion of the electroconductive armature 5. In order to decrease the magnetic reluctance offered to the ow of magnetic ux, a magnetic member 27 is spaced from the pole faces 21a, 2lb and Zic to provide air gaps between the member 27 and the pole faces. The elcctroconductive armature 5 passes thro-u gh these air gaps.

The magnetic member 27, lille the magnetic structure Zi, may be constructed of soft magnetic animations, such as soft iron, each having a shape similar to that illustrated in Fig. 2.

When energized, the winding 23 produces a magnetomotive force which directs agnetic nur: components through parallel paths. One of the paths includes the pole piece Z'B, the pole piece EEA, a portion of the magnetic member 27, and the air gaps betwee the magnetic member 27 and the pole faces 21a and 2lb. The second path includes the pole piece 21B, the pole piece 21C, a portion of the magnetic member 27 and the air gaps between the magnetic member and the pole faces 2lb and Zic.

in order to establish a phase displacement between Certain of the magnetic fluxes, a closed lagging winding 29 surrounds the pol` piece ZiA. Alt rough the lag'ring winding may be a continuous and fixed closed windin it will be assumed that the winding is closed through a switch 3i, and that the number' of turns in the winding are adjustable by means of an adjustable tap 33.

Magnetic liuxes which flow between the magnetic niember 27 and the pole pieces 25A, 2lb and 23C are represented in Fig. 2 by vectors de., pb and de.

When the lagging winding 2li is closed through the switch 3l, the magnetic flux components traversing the clectroconductive armature 5 reach their maximum values in the same directions through the gaps in the order qta, b and 4ta. This produces a shifting magnetic field and applies a torque between the electromagnet and the electroconductive armature 5 which urges the portion of the armature in the gaps of the electromagnet from lett to right as viewed in Fig. 2. if the switch 3l is opened, the two symmetric parallel paths associated with the winding 23 produce similar magnetic flux components and no torque is applied between the electromagnet and the electroconduetive armature.

The switch 3l may representthe contacts a directional relay. lf power flows in one direction in the associated electrical circuit, the switch 3ft is closed to permit effective energization of the electromagnet 7. lf the power iiow is in the reverse direction, the switch 3l is opened to prevent operation of the relay R.

ln order to control the shape of the time curve of the relay R, at least one of the two magnetic paths offered to magnetic flux produced by current owing in theV winding 23 is adjustable. Preferably, both of the paths are independently adjustable. The` adjustments may be effected by provision of one or more adjustable magnetic elements A or B for each of the paths. The magnetic elements mayA take the form of plugs which are screw operated. For example, in Fig. 1 the plug A has a large magnetic head 39 with a stud 41 projecting from one end thereof. The stud 41 is in threaded engagement with a portion of the stator 1. The head 39 is constructed of soft magnetic material such as soft iron or steel. It is located within an opening provided in the magnetic structure 21 and is slidable through the opening in response to rotation of the plug. If desired, the head 39 may be spaced from the walls of the opening by a thin-walled nonmagnetic sleeve. For example, a thin plating of non-magnetic material such as copper, may be applied to the head 39 for this purpose.

It will be noted that each of the plugs, for example the plug B, varies the series magnetic reluctance of the magnetic path with which it is associated.

In a preferred embodiment of the invention, the plugs A and B are employed in the positions shown in Fig. 2. It will be understood that the openings provided in the magnetic structure 21 to receive the plugs leave bridges A1, A2, B1 and B2 which saturate for low values of magnetic tlux therethrough. When the plugs A and B are introduced into their associated openings, they shunt magnetic ilux around their associated bridges and thus alter the magnetic reluctances of the paths which contain the plugs.

It will be recalled that taps such as the taps 23A, 23B are provided on the energizing winding 23 for the purpose of permitting adjustment of the minimum current required to trip the relay. In conventional practice, each of the taps would be rated at a specific minimum tripping current value. However, in practice, it is ditiicult to obtain accurate minimum tripping current values from selection of the taps alone.

In order to provide a further adjustment of the minimum tripping current values, the present invention provides a closed winding which surrounds part or all of the magnetic uX produced by the energizing winding 23. Thus in Fig. 2, the closed winding comprises a coil 45 which surrounds the pole piece 21B and which has its terminals connected across an adjustable impedance which is preferably an adjustable resistor 47. The winding 45 serves essentially as the secondary winding of a transformer wherein the winding 23 represents the primary winding. Because of the coupling between the two windings, a current flows in the winding 45 which produces a magnetomotive force acting in opposition to the magnetomotive force produced by the energization ofthe winding 23. The value of the magnetomotive force produced by the winding 45 may be controlled by adjustment of the magnitude of the resistor 47. Since the magnetic flux flowing in the pole piece 21B is determined by the resultant of the magnetomotive forces produced by the windings 23 and 45, the adjustable resistor 47 provides a convenient adjustment for the amount of magnetic flux owing in the pole piece 21B for each energization of the winding 23. It will be noted that the resistor 47 provides in effect a continuous Vernier adjustment which may have a range sulhcient to take care of any deviations which may be encountered in practice from the rated minimum tripping currents represented by the taps of the winding 23.

If desired, the closed winding may be associated with other portions of the magnetic structure. Thus, in Fig. 3 the coil 45 surrounds the pole piece 21C. If the closed windings surrounding the pole pieces 21A and 21C of Fig. 3 were exactly similar, it is clear that no torque would be applied by the electromagnet to the associated annature. For this reason, the coil 45 is proportioned to provide a lagging effect smaller than that produced by the winding 29. The reduction may be obtained in any suitable manner as by employing a smaller number of turns in the coil 45 than in the winding 29 or by reducing the cross section of the conductor employed in the coil 45 or by adopting both expedients. The lagging effect of the coil 45 also is reduced by inserting the resistor 47 (which may be continuously adjustable) in circuit therewith. By adjustment of the resistor 47 in Fig. 3, the lagging effect of the coil 45 and the torque applied to the associated armature may be adjusted over a range sucient to compensate for deviations which may be encountered from the rated values represented by the taps of the winding 23.

Although various constructions may be employed for the coil 45 and the resistor 47, a suitable construction is illustrated in Figs. 4 and 5. ln these figures, the coil 45 is represented by a copper coil 49 which, for example, may have a single turn terminating in terminals 49A and 49B. The coil 49 may be insulated from the pole piece 21C in any suitable manner as by means of an insulating sleeve 49C. However, with a single-turn copper Coil, the resistance of the coil is so low compared to that of paths resulting from contacts between the coil and the magnetic structure that the sleeve 49C may be omitted.

The pole piece 21C also is surrounded by a coil 51 which is constructed of a material having high resistance, such as a nickel-iron resistance alloy. As shown clearly in Fig. 5, the terminals 51A and 51B of the coil 51' are bent parallel to the pole piece 21C to engage respectively the terminals 49A and 49B. The terminal 51A and the terminal 49A may be secured to each other in any suitable manner as by brazing. Similar comments apply to the junction of the terminals 49B and 51B.

It will be observed that in Figs. 4 and 5 the terminals 51A and 51B are parallel to each other and are bridged by an electroconductive clamp 53. Thus, the clamp 53 may comprise a pair of copper plates 53A and 53B which are positioned on opposite sides of the terminals 51A and 51B. A machine screw 53C has a threaded portion which passes freely through the plate 53B into threaded engagement with the plate 53A. By manipulation of the screw, the clamp may be secured to the terminals or released therefrom.

As the clamp 53 is moved downwardly from the position which it occupies in Figs. 4 and 5, the resistance connected across the terminals 49A and 49B is progressively decreased in value. Consequently, such resistance may be adjusted as required.

It will be noted that the junction of the terminals 51A and 49A is substantially above that of the terminals 51B and 49B. This staggering of the junctions assures a smooth variation in the value of the resistance as the clamp 53 approaches the coil 49.

The material in the coil 51 preferably has a resistance which is so large that the coil has a negligible effect on magnetic ux passing through the associated pole piece even though the clamp 53 is positioned adjacent the coil 51. Although the coil 51 need not be employed and need not surround the pole piece 21C, the construction illustrated in Figs. 4 and 5 is desirable for mechanical support reasons. If desired, the coil 51 may be insulated from the pole piece. However, because of its high resistance, such insulation is not required.

Although the invention has been described adequately above, it will be helpful to consider the present understanding of the operation of the invention. In Fig. 8, a number of curves have been plotted on coordinates wherein ordinates represent torque acting between the rotor and stator of the relay and wherein abscissae represent degrees of contact travel. The abscissa 0 represents the position of the movable contact 17 shown in full lines in Fig. 6. The abscissa 270 represents the position of the movable contact when it is in engagement with the fixed contact 19 of Fig. 6.

Let it be assumed initially that the spring 15 of Fig. 6 applies a torque between the rotor and stator of the relay which is represented by the broken-line curve 2S in Fig. 8. It will be noted that when the movable contact occupies the position shown in full lines in Fig. 6, a substantial torque is applied by the spring to urge the movablecontact Vinto engagement with-the'stop v157B. VIf the curveZS is projected tothe left of the Zerodegree 'lineof' Fig. 8, it will intersect the zero torque lineat the point 62.

Let it be assumed next that theelectromagnet of'the 'relay-is energized with a constant energization yto produce avtorque acting between the rotor and stator which is represented by the curve 2E in Fig. 8. It'will be understood that the torques exerted by the springandbyl the electrc'im'agnet act in opposite directions between the rotor wand stator or the relay. However, in Fig. 8 all ofmthe torque curves are shown above the Zero torque line and represent the magnitudes of the various 'torques Because of the spiral configuration of the'disc or armature, the curve ZE has a slope. curves 2E and 2S intersect at a point Corresponding to 'fthe'contact position 64. If the curve 2E is projected suciently, ity will be found to intersect the zero torque line at a point u91.

Next, let it be assumed that the spring of Fig. 6 is"adjusted relative to the shaft 3 to produce a torque actingbetween the rotor and stator of the Vrelayivhich is represented in Fig. 8 by the broken-line curve 3S. For `present purposes, it will be assumed that the inner 'end-of the spring 3 is secured to a hub which is frictionally mounted on the shaft 3. By rotation of -the'hub on the shaft, the torque exerted between the rotor and stator by the spring may be adjusted. lt will be noted'in Fig. -8 that the curve 3S is a straight line which, if projected, intersects the zero torque line at a point 93. The curves 2S and 3S are parallel.

-If the energization of the electromagnet now is increased to produce a torque substantially balancing that of Athe curve 3S, it will be found that the torque exerted 'by the electromagnet may be represented by a curve 3E. 'This curve is a straight line which, if projected, intersects the'torque line at a point 31.

By inspection or Fig. 8, it will be noted that the minimum'tripping current of the relay does not remain coustant for all initial positions of the movable contact. For example, if the movable Contact initially occupies the Yposition'shown in full lines in Fig. jenergization of the electromagnet as shown by the entre 3E (Fig. 8) is in- ItWill'be' noted that the sufficient to overcome the spring bias and the rotor will -not move relative to the stator. However', it the movable contact is moved by the stop or time lever 7B to a posi tion shown in dotted lines 7A in Fig. 6, the movable contact starts from a position which is to the right of the dotted line 05 in Fig. 8. By inspection of the'curv'es, it

iwill be'seen that the torque represented by the curve 3E 'now isV suliicient to overcome the spring bias and the movable contact will be urged towards its associated iixcd contact with a resultant torque which increases gradually as the movable contact nears its associated lixed Contact.

ln order to provide a relay having a minimum tripping current which is independent of the position of the movable contact, the spring i5 of Fig. 6 may be adjusted to provide a bias represented by the curve 1S of Fig. 8. 'This curve is parallel to the curves 2S and 3S but if prol'jected intersects the zero torque line at the point 01.

The electromagnet now has a minimum tripping current which produces a torque represented by the curve 1E in Flg. 8. The curves iE and 1S substantially coincide.

Consequently, the minimum tripping current of the relay,

when so adjusted, is independent of the initial position of the'movable contacts.

A'suitable sequence for adjusting the relay may be set forth as follows: It will be assumed that-the lagging winding 29 of Figs. 2 and 3 is a iixed winding and is not employed for the purpose of adjusting the relay. It will be vassumed further that the tap on the/winding 23"which represents a minimum tripping current of` Lfamperes is selected. VWith the winding 23 energizedfthrough this Ttap, the control spring 15 is adjusteduntil lthe Asame 'minimum current is required to vmove -the'farmatu're clamp 53.

against-the'biasof the control springfromrsubstantially -anypoint-in the range of rotation of 'thearmature Such adjustment 'rnaybe -made by`ob`serving the minimum current required tomoveA the'armatu're when thearmature is adjacent'each endof itsrange of rotation. It will be assumed that with the selected tap representing a minimum trippingcurrent of 4 amperes, an actual current of 3.8 amperes sufrices to move the armature against the bias of the control spring.

As a rule, it is not essential that the minimum tripping currents match exactly=at the extreme ends of the range of movement ofthe armature. The amount of tolerance permissible depends on the specilicr application, but a small tolerance vis desirable. It will be understood Ythat the relayY now-fis adjusted to provide operating curves similar to the operating curves 1S and 1E of Fig. 8.

it will be recalled that although the tap representing a minimum tripping current of 4 amperes is being 'employed the actual minimum tripping current Vis assumed to'be of the order of 3.8'a`rnperes. In order to bring the actual minimum trippingcurrent to the desired value of 4 amperes, the resistance value of the resistor 47 (Fig. 2) is suitably adjusted. Thus, in Fig. 2, a decrease in the resistance'valueof the resistor 47 will raise the actual minimum tripping current 'from 3.8 amperes to the desired 4 amperes. Similar comments apply to the resistor 47 of Fig. 3. The desired variation in the resistance is obtained by suitable adjustment of the position of the If 'the resistor`47 is suitably adjusted, the armature'S will advance against the bias of the control spring when ther winding 23' is energized by a curve slightly in excess of 4 amperes, such as 4.02 amperes. If the energizing current thereafter is decreased to a value slightly less than 4 amperes, such as 3.98 amperes, the armature is returned by the control spring to its starting position.

The damping ofthe armature 5 now may be adjusted by suitable manipulation of the plug 13. It will be assumed that when the relay is energized by current having twicethe' magnitude of the current represented by the tapl in use, the relay should operate in 27 seconds from the position ofthe stop 17B corresponding to the greatest time delay. In order to adjust the relay, a current having a magnitude equal to twice that represented by the tap is passedthrough the winding Z3. The plug 13 then can be adjusted until the desired tripping time is obtained.

The plugs VA and'B now may be adjusted as desired. For example, the winding 23 'may be energized by a current having a magnitude which is twenty times that Vrepresented by the tap'in use. ln the specific case herein full-line curves CA 'and CB are time curves for a relay having the electromagnet of Fig. 3 adjusted for a minimum tripping current of 4 amperes. The time curve CA'is obtainedy with the plug A completely within the electromagnet Vand the plug B completely withdrawn from the electromagnet. The curve CB is obtained with the plug A completely withdrawn from the electromagnet and the plug B completely inserted in the electromagnet. It will be-understood that other time curves Vmay --be obtained by suitable manipulation of the plugs.

` lf'the relay represented in Fig. 3 is initially adjusted to produce a time curve CB and'thereafter has the coil 45 removedorpopen circuited, it will be found that a time lcurve'CC Y(Fig. 9)-isobtained. Furthermore, it

will 'bee fou'nd'that'for the"`specific 'relay' under consid- Q eration the minimum tripping current required decreases to a lower value such as 3.6 amperes.

Let it be assumed next that the relay represented in Fig. 3 initially is adjusted to provide the time curve CB (Fig. 9) and thereafter the resistance value of the resistor 47 is decreased to require a larger minimum tripping current such as 4.46 amperes. For the specific relay under consideration, it will be found that a time curve CE (Fig. 9) is obtained. If it is desired to operate on this time curve CE but to provide a minimum tripping current of 4 amperes, the number of turns in the energizing winding 23 (Fig. 3) may be increased sufticiently to reduce the minimum tripping current to 4 amperes. In this way, the range of adjustment of the time curve is materially increased. The change in the time curve as represented by the curve CE probably is due in part to increased saturation of the magnetic structure and in part to less efficient resultant phase splitting.

Returning now to the electromagnet of Fig. 3 which was adjusted to produce the time curve CB (Fig. 9), let it be assumed that the coil 45 of Fig. 3 is transferred to the position illustrated in Fig. l2. If the relay again is adjustedto provide a minimum tripping current of 4 amperes, a time curve CD (Fig. 9) `is obtained.

The curves of Fig. 9 all approach a common point which may, for example, be of the order of 27 seconds at two times minimum tripping current. The position of this point may be adjusted if desired by varying the damping force exerted by the damping magnet 9. It will be recalled that such variation in damping force may be obtained by adjustment of the plug 13 (Fig. l).

In Fig. 10, a modified construction is illustrated for the coil 45 and the resistor 47 of Fig. 3. This modification is a simple one and has been found to factory.

Referring in detail to Fig. 10, two spaced rigid supports 60 and 61 are provided. These supports have rectangular openings proportioned-to receive snugly therein the pole piece 21C. The support 60 may be constructed from a sheet of high resistance material or a sheet of insulating material, such as a phenolic resin. The support 60 has spaced openings 62 and 63 through which the legs 64 and 65 of an electroconductive hairpin HP pass. It will be noted that the closed end 66 of the hairpin HP is adjacent the support 60. On the opposite side of the support, the legs of the hairpin may be crimped at points 63A and 63B to prevent movement of the support 60 relative to the hairpin.

The support 61 is similar in shape to the support 60 except for the provision of a slot 68 which extends through one side ofthe support to provide terminals 69 and 70. The support 61 may be constructed of an electroconductive material, such as copper.

The terminals 69 and 70 have openings 71 and 73 through which the free ends of the legs 64 and 65 pass. The legs may be secured to the terminals to provide good electrical contact therewith in any suitable manner as by soldering the legs to the terminals.

The support 61 corresponds to the coil 45 of Fig. 3, whereas the legs 64 and 65 provide parallel conductors which take the place of the resistor 47. The legs 64 and 65 are provided with an adjustable bridge 75 which includes a U-shaped electroconductive member 76 having legs 76A and 76B which engage parallel faces of the pole piece 21C. A through bolt 77 passes through the legs 76A and 76B and may be adjusted to maintain the legs in sliding engagementwith the associated faces of the pole piece. Consequently, the pole piece guides the member 75. v

Each of the legs 76A and 76B is provided with notches for receiving the forked ends of a clamping bar 79. For example, the leg 76B has notches 76B1l and 76B2 for receiving the tines of the adjacent forked end of the bar 79. A cap screw 81 passes through the member 75 be entirely satisbetween the legs 64 and 65 of the hairpin for threaded reception in the bar 79. Consequently, by manipulation of the cap screw 81, the legs 64 and 65 may be clamped firmly between the bar 79 and the member '75. In order to adjust the resistance introduced by the legs 64 and 65 in series with the coil formed by the support 61, the cap screw 81 may be released to permit movement of the bridge 75 to any desired position.

It has been found that an adequate range of resistance may be provided if the hairpin HP is constructed of copper wire having suflicient rigidity to maintain its shape under the conditions of use. If greater resistance is desired, the hairpin may be constructed of copper wire having a smaller cross section, or it may be constructed of a higher resistance material.

Although the invention has been described with reference to certain specific embodiments thereof, numerous modifications thereof are possible. Consequently, the embodiments herein set forth are to be construed in an illustrative rather than in a limiting sense.

I claim as my invention:

1. In a time-delay induction relay device responsive to an alternating quantity, a magnetic structure having first, second and third pole pieces, field-producing means cooperating with the magnetic structure to direct magnetic lux through said pole pieces to develop a shifting magnetic field, said field producing means comprising a winding surrounding the first pole piece and effective when energized for directing magnetic flux in parallel through the second and third pole pieces, an electroconductive member mounted for movement relative to the magnetic structure under the inuence of the shifting magnetic field, said pole pieces having pole faces adjacent the electroconductive member for directing thereto magnetic flux having components substantially transverse to the electroconductive member, and closed circuit electroconductive means associated with only one of the pole pieces for continuously and uniformly altering the time phase of magnetic ux passing therethrough when the winding alone is energized, said closed-circuit electroconductive means being adjustable for varying the effect thereof on magnetic ux passing through the associated pole piece, and damping means for opposing rotation of the electroconductive member by an adjustable force which varies as a function ot' the rate of rotation of the electroconductive member.

2. A device as claimed in claim 1, in combination with means for varying the magnetic path for magnetic flux traversing the second pole piece.

3. in a time-delay induction relay device responsive to an alternating quantity, a magnetic structure comprising first, second and third pole pieces having pole faces disposed substantially in alignment in a common plane, a magnetic member spaced from said pole faces to define an airgap between the member and each of the pole faces, an electroconductive armature mounted for rotation relative to the magnetic structure about an axis, said electroconductive armature having a portion spaced from the axis and positioned for movement through the airgaps, a winding on the first pole piece, said magnetic structure being effective for directing magnetic flux produced by the widing when energized through the second and third pole pieces in parallel to operate the armature, and an adjustable closed-circuit coil linked with the magnetic linx traversing only the second pole piece for adjustably lagging such magnetic flux to produce a shifting magnetic field in the air gaps having magnetic flux components entering a surface of the armature in directions substantially transverse to the surface when the winding is energized by alternating current, said closed circuit coil having a closed circuit independent of the position of the electroconductive armature, in combination with damping means for damping rotation of the armature.

4. A device as claimed in claim 3 in combination with means for independently adjusting the magnetic paths offered to the magnetic fluxes traversing the second and third pole pieces.

5. A device as claimedvinfclaim 3, wherein a first magnetic flux component produced by energization of the winding traverses a first magnetic path which includes in series the first pole piece, the second pole piece, a portion of the magnetic member and the airgaps between the magnetic member and the first and second pole pieces, and wherein a second magnetic flux component produced by cnergization of the winding traverses a second magnetic path which includes the first pole piece, the third pole piece, a portion of the magnetic member' and the airgaps between the magnetic member and the first and third pole pieces, biasing means for biasing the armature against operation, andadjusting means for adjusting the magnetic reluctancerrof at least one o said magnetic paths, said'adjusting means comprising a variable magnetic section located in one of said magnetic paths.

6. A device as claimed in claim 5, wherein the adjusting means comprises a separate adjustable element for independently adjusting the magnetic reluctance of each of the magnetic paths.

7. ln a. time-delay induction relay device responsive to an alternating quantity, a magneticstructure having first, secondand third pole pieces, field-producing means cooperating with the magnetic structure to direct magnetic linx through said pole pieces to develop a shifting magnetic field, said field producing means comprising a winding surrounding the first pole piece and effective when energized for directing magnetic liux in parallel through the second and thirdv pole pieces, an electroconductive member mounted for movement relative to the magnetic structure, said polerpieces having pole faces adjacent the electroconductive member for directing thereto magnetic flux having components substantially transverse to the electroconductive member, closed winding means surrounding only the second pole piece of said three pole pieces to establish a closed circuit independent of the position of the electroconductive member, said closed winding` means being adjustable independently or" the position of the electroconductive member for varying the laggingthcreby of magnetic liux passing through the second pole piece, and a closed winding surrounding only the third pole piece of said three pole pieces for lagging magnetic flux passing through the third pole piece to the same extent for all' positions of the electroconductive member'and for all adjustments of the closed winding means, and damping means for opposing rotation of the electroconductive member by an adjustable force which varies as a function of the rate of rotation of the electroconductive member.

8. in a time-delay induction relay device responsive to an alternatingV quantity, a magnetic structure having first, second 4and third pole pieces, field-producing means cooperating with the magnetic structure to direct magnetic flux through said pole pieces to develop a shifting magnetic field, said field producing means comprising a winding; surrounding theV first pole piece and effective when energized for directing. magnetic linx in parallel through the second and third pole pieces, an electroconductive member mounted for movement relative to the magnetic structure, said pole pieces having pole faces adjacent the electroconductive member for directing thereto magnetic flux having components substantially ansvcrse to the electroconductive member, closed windnicanssar 'ounding only the second pole piece of said pole pieces, said closed winding means being -lfle for varying the lagging thereby of magnetic passing through the second pole piece, andY a closed winding surrounding only the third pole piece of said three pole pieces for lagging magnetic liux passing through thethird pole piece to the same extent for all positions of the electroconductive member and for all adjustments of the closed winding means, and damping means for opposing rotationy Vof the electroconductive member by an adjustable'force which varies as a function of the rate of rotation of the electroconductive member, biasing means for biasing the electroconductive member against rotation relative to the magnetic structure in a first direction, damping means for opposing rotation of the electroconductive member in the first direction relative to the magnetic structure with a force which varies as function of the rate of rotation of the electroconductive member, and means for independently varying the magnetic paths for the magnetic fluxes traversing the second and third pole pieces.-

9. ln an induction time-delay relay, an electromagnet having an airgap and having means effective when energized producing magnetic liux creating a shifting magnetic field in the airgap, an electroconductive armature mounted for rotation relative to the electromagnet` and having a portion-.spaced from the axis of rotation positioned in the airgap, said portion being positioned substantially transversely relative to at least a part of the magnetic linx of said magnetic field, biasing means for biasing` the armature towards a predetermined position relative-to the electromagnet with a torque which varies as the armature rotates relative to the electromagnet, said armature having a configuration presenting a varying effective portion to said airgap as the armature rotates to compensate substantially for the variation in the bias exerted by said biasingfmeans, said electromagnet comprising a first winding, a first magnetic path for directing a first magnetic linx produced by the first Winding when energized by alternating current into the airgap, a second magnetic path for directing a second magnetic linx produced by the first winding when energized into the airgap, closed winding means linked with the first magnetic path for lagging magnetic flux traversing the first path to alter the phase relationship between the first and second magnetic fluxes, said closed winding means being adjustable for adjusting the lagging of magnetic flux traversing the first path independently of the magnetic flux traversing theY second path and independently of the position ofv the electroconductive armature, and adjustable damping means for damping rotation of the armature relative to' theelectromagnet.

l0. ln an induction time-delay relay, an electromagnet having an airgapl and having means effective when energized for producing magnetic linx creating a shifting magnetic eld in theA airgap, an electroconductive armature mounted for rotation relative'to the electromagnet and having a portion spaced from the axis of rotation positioned in the airgap, said portion being positioned substantially transversely relative to at least a part of the magnetic flux of said vmagnetic field, biasing means for biasing the armature towards a predetermined position relative to the electromagnet with a torque which variesy as the armature rotates relative to the electromagnet, said armature having a configuration presenting a varying effective portion to said airgap as the armature rotates to compensate substantially for the variation in' the bias exerted by said biasing means, said electromagnet comprising a first winding, afirst magnetic path for directingl a first magnetic liux produced by the rst winding when energized by alternating current into the airgap, a second magnetic path for directing a second magnetic flux produced by the first windingwhen energized into the airgap, closed winding means linked with the first magnetic path for lagging magnetic fiux traversinggthe first path to alter the phase relationship between the first and second magnetic liuxes, said closed winding means being adjustable for adjusting the lagging of' magneticliux traversing the first path independently ofl thel magnetic fluxV traversing the second path and independently of the position of the electroconductive armature, and closed windingmeans r linked withl the'secondrmagnetio path forlagging magnetic fLux traversing the second path, the magnetic fluxes 1,740,536 Breisky Dec. 24, 1929 traversing said two paths cooperating to establish said 2,238,626 Crichton et al Apr. 15, 1941 shifting magnetic field, and adjustable damping means for 2,419,396 Frisk Apr. 22, 1947 damping rotation of the armature relative to the electro- 2,488,443 Sonnemann Nov. 15, 1949 magnet' 5 FOREIGN PATENTS References Cited in the le of this patent 337,119 Great Britain Oct. 30, 1930 390,922 Great Britain Apr. 30, 1933 UNITED STATES PATENTS 550,795 France Apr. 29, 1922 1,702,454 Todd Feb. 19, 1929 10 1,714,940 Biermanns May 28, 1929 

